1. Technical Field
The present invention relates to a circuit board that is used for a variety of electro-optical devices such as a liquid crystal device, and further relates to the electro-optical device that is provided with the above-mentioned circuit substrate. In addition, the present invention relates to an electronic apparatus that is provided with such an electro-optical device having the above-mentioned circuit substrate. A non-limiting example of an electronic apparatus to which the present invention relates is a liquid crystal projector.
2. Related Art
A typical electro-optical device has, over its substrate, a plurality of pixel electrodes, a plurality of scanning lines for selectively driving the pixel electrodes, a plurality of data lines, and a plurality of thin film transistors (TFT) each of which functions as a pixel-switching element. An electro-optical device having such a configuration is capable of operating in an active-matrix driving scheme. A lamination structure that is made up of a plurality of functional films deposited one on another is formed over the substrate of an electro-optical device, where, in such a lamination structure, the functional films include electro-conductive films, semiconductor films, and the like, that constitute scanning lines, data lines, TFTs, and the like so as to correspond to each one of individual pixels. For each pixel, the pixel electrode is formed at the uppermost layer, though not necessarily limited thereto, of the lamination structure.
In some related-art lamination structure of a circuit board for an electro-optical device, for example, as disclosed in JP-A-2001-281684, a storage capacitor is formed between a TFT and a pixel electrode in order to enhance contrast thereof. The storage capacitor is made up of a lower capacitor electrode, an upper capacitor electrode, and a dielectric film that is sandwiched between the lower capacitor electrode and the upper capacitor electrode. In the lamination structure of the related art, the upper capacitor electrode, which is provided at a layer over the counterpart layer of the lower capacitor electrode, is electrically connected to the TFT via a contact hole that is formed to penetrate through the dielectric film deposited immediately under the upper capacitor electrode.
In the manufacturing process of an electro-optical device of the related art, the formation of a contact hole is performed as follows. Before the formation of an upper capacitor electrode on a dielectric film, a resist is applied to the dielectric film so as to form a resist coating thereon. Then, etching treatment is applied to the dielectric film while using the resist film as a mask. In this way, a contact hole is bored through the dielectric film.
In order to manufacture the lamination structure of the related art described above, it is necessary to form a resist mask on the surface of a dielectric film in the process of forming a contact hole that goes through the dielectric film. In addition, it is also necessary to remove the resist mask after the formation of the contact hole. For this reason, there is an adverse possibility that the surface of the dielectric film might become polluted by any residual resist that remains without being removed completely. As an example of another possible risks, the actual film thickness of the dielectric film might deviate from its designed ideal film thickness because the surface of the dielectric film might get “eroded away” in such a contact-hole formation process. Generally speaking, a dielectric film requires precision in surface control; that is, the surface of a dielectric film is required to meet strict design criteria in order to ensure the reliable performance of a storage capacitor. However, if the surface of a dielectric film is subjected to some kind of treatment such as the above-described contact-hole formation treatment before the formation of an upper capacitor electrode, it is possible that the surface of the dielectric film gets degraded in quality because of the pollution or the film thickness deviation thereof as described above, which poses a technical problem that has not yet been solved by the related art. In other words, the lamination structure of the related art described above has a risk in that the above-described possible degradation in the quality of a dielectric film causes a decrease in the withstanding pressure of the dielectric film. As a disadvantageous consequence thereof, a leakage current might increase.